Boric Acid Glass Research Articles

Stabilisation of solid-state cubic ammonia confined in a glass substance at ambient temperature under atmospheric pressure.

Ammonia, a widely available compound, exhibits structural transitions from solid to liquid to gas depending on temperature, pressure, and chemical interactions with adjacent atoms, offering valuable insights into planetary science. It serves as a significant hydrogen storage medium in environmental science, mitigating carbon dioxide emissions from fossil fuels. However, its gaseous form, NH3(g), poses health risks, potentially leading to fatalities. The sublimation pressure (psub) of solid cubic ammonia, NH3(cr), below 195.5 K is minimal. In this study, we endeavoured to stabilise NH3(cr) at room temperature for the first time. Through confinement within a boric acid glass matrix, we successfully synthesised and stabilised cubic crystal NH3(cr) with a lattice constant of 0.5165 nm under atmospheric pressure. Thermodynamic simulations affirmed the stabilisation of NH3(cr), indicating its quasi-equilibrium state based on the estimated standard Gibbs energy of formation, . Despite these advancements, the extraction of H2(g) from NH3(cr) within the boric acid glass matrix remains unresolved. The quest for an external matrix with catalytic capabilities to decompose inner NH3(cr) into H2(g) and N2(g) presents a promising avenue for future research. Achieving stability of the low-temperature phase at ambient conditions could significantly propel exploration in this field.

Reduction of Harmful Emissions from Domestic Power Generator Usage in Nigeria -A Tribological Approach

Worldwide concern for the release of harmful emission from Internal Combustion (IC) engines requires the optimization of the quantity of fuel used, types of fuel blend used and type of lubrication utilized. In Nigeria, the electrical power requirements of many households rely more on alternative sources such as Solar systems and fossil fuel-powered generators. The use of these generators is known to produce exhaust fumes that are harmful to humans and the environment. This study investigated the effect of using two different commercially available lubricating oils for gasoline-fueled power generators for domestic applications in comparison to used oils. These are SAE 40 and SAE 20W50. The effect of Boron additive on the two oil brands and used oils (or aged oils) at different speeds on emission from the exhaust stream from the generator was investigated. This is to provide a better understanding of the behavior of Boron additive with SAE 40, SAE 20W50, and aged oils. The study also compared results of torque and emission measurements from oils containing boron to oils without the Boron additives at different speeds. The instruments used to carry out the measurement are a digital tachometer, torque meter (contact type), and 5-gas exhaust analyzer. Results from this study indicated a general decrease in torque with increased speed for all the lubricating oils. This is in agreement with the results of similar studies on torque outputs from IC engines with increasing speeds. However, oils lubricated with Boron additives minimized this loss at a different speed more in SAE 20W50, SAE 40 than in used oils. Carbon monoxide emission from these results indicated that generators lubricated by aged oils are highest at all speed ranges irrespective of Boron additive inclusion. Cleanliness from a gasoline-powered generator is possible if Boron additive is added to lubricating oils. The concentration of NOx emission was found to rise considerably only when operated at the highest speed for aged oils. The results of this study indicated that tribofilms formed by boron-containing oils played a role in preventing torque reduction or power loss and CO emissions from power generators for domestic use. This behavior was attributed to the friction-reducing boric acid and wear resistance borate glass contained within the trilayer. However, tribofilms formed by used oils on tribological parts of the engine gave poor torque reduction results in comparison to that provided by fresh oils. This indicated that when lubricating oils in power generators used in homes are aged beyond the recommended interval for replacement, substantial power loss and harmful emissions are released to the surroundings.

Third order optical nonlinear studies and its use to estimate thickness of sandwiched films of tetra-phenyl porphyrin derivatives

Third-order nonlinear optical properties of tetra-phenyl porphyrin (H[Formula: see text]TPP) derivatives viz., H[Formula: see text]TPP(OH)[Formula: see text] and Zn(II)TPP doped in boric acid glass thin films were measured using single beam Z-scan and forward degenerate four-wave mixing (DFWM) techniques. Excited state lifetimes and absorption cross-sections were estimated from these experiments. Thickness of the porphyrin doped sandwich glass films were determined using DFWM technique for the first time. The values of nonlinear refractive index ([Formula: see text]) obtained for these systems are are found to be sensitive to the nature of substituents in porphyrin molecule. These results are interpreted in terms of delocalized [Formula: see text] electrons contributing to the third-order optical nonlinearity.

Study of spatial rings in TPPOH4 doped in boric acid glass

Single beam optical nonlinearity is studied in TPPOH4 doped in boric acid sandwiched films between two microscope glass slides at three different molar concentrations (4×10−4M, 1×10−4M, 5×10−5M). It shows absorption peak at 700nm with bandwidth of 70nm. We have used diode laser output at 671nm to probe resonant optical nonlinearities. We have observed interesting phenomena of formation of spatial concentric rings centered on the z-axis of the sample. To our knowledge this is first such observation of spatial rings in these systems. We have carried out studies to separate the contribution to the ring formation due to absorptive/refractive optical nonlinearity and the thermal nonlinearity.

Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

Laser Phosphoroscope and Applications to Room-Temperature Phosphorescence

A simple phosphoroscope with no moving parts is described. In one scan the total luminescence, the long-lived phosphorescence, and the short-lived fluorescence can be determined. A 50% duty cycle excitation from a diode laser is used to excite the sample, and from the digitized waveform the phosphorescence is extracted from the off period, the total emission from the full cycle, and the fluorescence from the on period corrected for the phosphorescence contribution. The performance of the system is demonstrated using room-temperature phosphorescence of organic dyes in boric acid glasses, a multi-emissive boron-polymer dye, and a europium chelate.

Modulated optical phase conjugation in rhodamine 110 doped boric acid glass saturable absorber thin films

The optical phase conjugation signal in nearly nondegenerate four wave mixing was studied using a rhodamine 110 doped boric acid glass saturable absorber nonlinear medium. We have demonstrated a narrow band optical filter (2.56±0.15Hz) using an optical phase conjugation signal in the frequency modulation of a weak probe beam in the presence of two strong counterpropagating pump beams in rhodamine 110 doped boric acid glass thin films (10−4m). Both the pump beams and the probe beam are at a wavelength of 488nm (continuous-wave Ar+ laser). The probe beam frequency was detuned with a ramp signal using a piezoelectric transducer mirror.

Narrow band optical filter in fluorescein doped boric acid glass saturable absorber thin films

We demonstrate narrow band optical filter like frequency response with full width half maximum (FWHM) of nearly (1.75 ± 0.25) Hz in fluorescein doped boric acid glass films [10 −4 M], using modulated optical phase conjugation and a nearly non-degenerate four wave mixing technique. Modulated optical phase conjugation signals are described in the limit of a weak probe and relatively strong pump beams. Both pump beams are of nearly equal intensity at a wavelength of 514.5 nm from a continuous-wave Ar + laser. The probe beam frequency has been detuned with a ramp signal using a piezo electric mirror.

Laser induced moving dynamic grating in fluorescein doped boric acid glass thin films (10 −4 M)

Laser induced moving dynamics grating has been studied in fluorescein doped boric acid glass films in the limit of a weak probe and a relatively strong pump. The results have been interpreted in terms of the four-level description of a saturable absorber. Good agreement has been obtained in the experimental and the fitted results. Estimated values of the non-linear parameters such as the saturation intensity, refractive index, and also the response time of the optical non-linearity have been obtained at different strong pump beam intensity.

Two-coherent-wave coupling in Rhodamine 110-doped boric acid glass solid films

We report the energy-transfer efficiency in a saturable absorber nonlinear media by two-coherent-wave coupling using the Doppler shift. Intensity-dependent nondegenerate two-beam coupling has been studied in Rhodamine 110-doped boric acid glass films. Two beams have been described in the limit of a weak probe and a relatively strong pump at the wavelength 488 nm from a continuous-wave Ar+ laser. The results have been interpreted in terms of the four-level description of a saturable absorber. We obtained good agreement between the experimental and the theoretical results. Estimated values of the nonlinear parameters such as the saturation intensity, refractive index, and the response time of the optical nonlinearity have been obtained at different pump beam intensities for the first time, to our knowledge, in the Rhodamine 110-doped film.

Measurement and theoretical characterization of electronic absorption spectrum of neutral chrysene (C 18H 12) and its positive ion in H 3BO 3 matrix

The ultraviolet and visible spectrum of chrysene and its radical cation formed by ultraviolet irradiation were measured in boric acid glass at room temperature. The theoretical electronic absorption spectrum of any polycyclic aromatic hydrocarbon (PAH) in boric acid matrix is calculated for the first time using semi empirical methods. Earlier reported theoretical results of electronic spectrum are calculated in free state and the results are compared with the spectrum of aromatic systems in glassy or other matrices. The interaction between the trapped PAHs (neutral and ions) and its environment induces strong perturbations of the energy levels which results in large shifts of the electronic transitions as compared to the ideal case of a free, isolated PAH molecule. This shifting due to perturbation has largely been ignored in earlier calculations, while comparing the calculations with the experimentally measured spectrum, in other matrices. The spectrum of singlet and doublet state of chrysene are computed in aqueous medium and also in free state to estimate the spectral shift. Several other geometric (bond length and bond angles) and spectroscopic parameters of chrysene like difference of HOMO–LUMO, ionization potential, dipole moment and polarizability are calculated using semi empirical methods, namely Austin Model 1 (AM1) and Parametric Method 3 (PM3). To get an idea about how the symmetry of chrysene molecule varies upon ionization, the mean polarizability ( α) as well as its tensor components α xx , α yy and α zz are calculated within a field of 0.005 a.u. The lasing action in neutral chrysene and in its cationic form is also discussed for the first time.

Ultrafast Studies on the Photophysics of Matrix-Isolated Radical Cations of Polycyclic Aromatic Hydrocarbons

Ultrafast relaxation dynamics for photoexcited PAH cations isolated in boric acid glass have been studied using femtosecond and picosecond transient grating spectroscopy. With the exception of perylene+, the recovery kinetics for the ground doublet (D0) states of these radical cations are biexponential, containing fast (<200 fs) and slow (3−20 ps) components. No temperature dependence or isotope effect was observed for the fast component, whereas the slow component exhibits both the H/D isotope effect (1.1−1.3) and a strong temperature dependence (15 to 300 K). We suggest that the fast component is due to internal Dn to D0 conversion and that the slow component is due to vibrational energy transfer (VET) from a hot D0 state to the glass matrix. The observed rapid, efficient deactivation of the photoexcited PAH cations accounts for their remarkable photostability and has important implications for astrochemistry because these cations are the leading candidates for the species responsible for the diffuse interstellar bands (DIB) observed throughout the galaxy.

Nonlinear absorption of light: two-photon absorption and optical saturation in metalloporphyrin-doped boric acid glass

Abstract The nonlinear absorption of five metal TMPPs (TMPP: tetrakis-(3,4,5-trimethoxyphenyl)porphyrin) doped in boric acid glass are measured with the linear polarized nanosecond laser pulses at different wavelengths by Z-scan; the two-photon absorption (TPA) is dominant in the near infrared, while the characteristic of saturation absorption (SA) is observed close to the Q(0,0) band of porphyrin. The symmetry allowed two-photon π*←π transitions are suggested to be 1 B 1 g * ← S 0 and 1 B 2 g * ← S 0 , with the cross-sections δ ranging from 25×10−50 to 114×10 −50 cm 4 s / photon . We analyze the property of SA with a four-level system, and find that the magnitudes of excited-state absorptivity and saturation intensity are not affected by changing the central metal ion in these experiments.

Nonlinear Light Absorption in Porphyrin Derivatives Including the Complexes of the IIIa Metal Group

AbstractThe nonlinear absorption properties of GaClTMPP, InClTMPP and TlClTMPP (TMPP: tetrakis‐(3,4,5‐trimethoxyphenyl)porphyrins) doped in boric acid glass are probed using the Z‐scan technique at different wavelengths. The characteristc of reverse saturable absorption (RSA) is observed at 532 nm, while the two photon absorption (TPA) is dominated at several wavelengths from 840 to 1350 nm. We find that the excited state absorption cross section σex at 532 nm is enlarged along a series of the central metal ions: Ga(III)Cl &lt; In(III)Cl &lt; Tl(III)Cl, and the two‐photon allowed transitions at near infrared are proposed to be 1B*1g ← S0 and 1B*2g ← S0

Modeling absorption in saturable absorbers

Non-linear absorption in boric acid glass films with 10 −4 M concentration of fluorescein and rhodamine 6G was measured with beam intensity variation covering six orders of magnitude. The non-linear absorption in these systems has been interpreted in terms of the four-level model of saturable absorbers. Optimum values of the film parameters have been obtained. Convergence problems encountered in the numerical solutions were successfully overcome.

Non-degenerate two wave mixing in R6G doped boric acid glass films

Two beam coupling has been studied in R6G doped boric acid glass films in the limit of a weak probe and a relatively strong pump. The results have been interpreted in terms of the four level description of a saturable absorber. Good agreement has been obtained between the experimental and the theoretical results. Estimated values of the non-linear parameters such as the complex refractive index, the saturation intensity and the response time of the optical non-linearity have been obtained.

Nonlinear optical studies in tetraphenyl-porphyrin-doped boric acid glass using picosecond pulses

We report the results of our studies on the nonlinear optical response of thin films of tetraphenyl porphyrin doped in boric acid glass for picosecond-duration pulses. The fluence-dependent transmission measurements show that the sample exhibits reverse saturation behavior at 532 nm and saturable absorber action at 683 nm. By fitting the nonlinear transmission data at these wavelengths to a rate equation model, values for σSe and σL the excited singlet and ground state cross sections were obtained. The large value (≈8) for σSe/σL makes it a potential material for optical limiting at 532 nm, whereas at 683 nm the ratio σL/σSe≈4.3. Intensity dependence of degenerate forward four-wave mixing at 683 nm was also investigated to establish the order and magnitude of the nonlinearity. The forward four-wave mixing signal at 683 nm showed a cubic dependence on the input intensity, establishing the third-order nonlinearity. A value of 4×10-12 esu for the third-order susceptibility |χ(3)| was estimated from the measured efficiency. The time response of the nonlinearity was measured by the pump-probe transmission experiment, resulting in a decay constant of about 1.8 ns for the repopulation of the ground singlet state at 683 nm.

Photoacoustic Spectroscopic Studies of Mono-Substituted Naphthalene Molecules

The present paper deals with the Photoacoustic (PA) studies of mono-substituted (hydroxy) naphthalene molecules, namely 1-naphthol and 2-naphthol in boric acid glass in the region 250–400 nm. The electronic transitions of these molecules observed experimentally, have been interpreted using the optimised geometries and CNDO/S-CI method. Assignments of observed electronic transitions are made on the basis of singlet-singlet and singlet-triplet transitions. The PA spectra of 1-naphthol and 2- Maphthol are compared with its parent molecule i.e. naphthalene molecule, in terms of charge transfer character of -OH group and polarization of molecules. It is observed that the non-radiative transitions in mono-substituted naphthalene molecules shift towards the higher wavelength region when compared with naphthalene molecule, which may be attributed to increase in the charge density in the substituted ring.

Investigation of the Excited-State Dynamics of Radical Ions in the Condensed Phase Using the Picosecond Transient Grating Technique

A study of the dynamics of ground-state recovery of the perylene radical cation (Pe•+), of perylene radical anion (Pe•-), and of anthraquinone radical anion (AQ•-) is reported. In boric acid glass, the excited-state lifetime of Pe•+ is 35 ± 3 ps, while in concentrated sulfuric acid, it is smaller than 15 ps, the time resolution of the experimental setup. The excited-state lifetime of Pe•+, Pe•-, and AQ•- generated by photoinduced intermolecular electron-transfer reaction in MeCN is shorter than 15 ps. In the case of Pe•-, the uncomplete ground-state recovery is ascribed to the occurrence of electron photoejection. The free ion yield in the intermolecular electron-transfer reaction between 9,10-dicyanoanthracene (DCA) and two electron acceptors was measured in a two-pulse experiment, where the second pulse excited the ensuing DCA•-. This excitation has no influence on the magnitude of the free ion yield, indicating a short excited-state lifetime of DCA•-* relative to the time scale of back electron transfer and ionic dissociation. A red emission, ascribed to the fluorescence of protonated Pe, was detected in boric acid glass and sulfuric acid. No fluorescence that could be clearly ascribed to Pe•+* could be observed.

Resonant Nonlinear Optical Studies on Porphyrin Derivatives

The nonlinear optical properties of three porphyrin derivatives (T3,4 BCEMPP, T4 CEMPP and TPP) doped in boric acid glass were probed using the Z-scan technique at different argon-ion laser wavelengths. The nonlinear transmission characteristics of T3,4 BCEMPP and T4 CEMPP exhibit saturable absorption at 457.9 nm and 476.5 nm while these are dominated by excited state absorption at 488.0 nm. However, in the case of TPP, the excited state absorption dominates the nonlinear characteristics except at 457.9 nm. The experimental observations are explained by using the four-level saturable absorber model. Saturation intensity, excited state absorption cross-section, light-induced changes in the absorption and the refractive index along with its sign were determined at these argon-ion laser wavelengths. Furthermore, optical limiting characteristics of these samples were studied. The observed limiting action is consistent with the Z-scan studies.